Shorting plug



May 4, 1965 R. B. ASHBY SHURTING PLUG Filed April 18, 1962 .n illf l llf FIG.2

FIG.

FIG.

FIG

INVENTOR ROBERT B. ASHBY AGENT United States Patent 3,182,277 SHORTING PLUG Robert B. Ashby, Alexandria, Va., assignor to Atlantic Research Corporation, Fairfax County, Va., a corporation of Virginia Filed Apr. 18, 1962, Ser. No. 188,449 Claims. (Cl. 339-19) This invention pertains to apparatus for the electrical shorting of an electrical connector and in particular pertains to a plug for electrically shorting the male mating elements of an electrical connector.

During the handling of electrically actuated ignition and explosive devices, there is a danger of premature actuation due to current flow caused, for example, by radio-frequency induction or the presence of static electricity. Accordingly, safety devices and procedures have been devised to reduce or eliminate premature actuation.

One procedure has been to short out the leads attached to the ignition device whereby any current that develops in the leads is shunted around the ignition device. In its simplest form this shorting can be accomplished by twisting the ends of the leads together as is often done with the leads of blasting caps used with dynamite. However, there are situations where the leads are not susceptible to such treatment a where they terminate in a plug or socket. Such a situation is often found in the manufacture of devices such as squibs or igniters, where these devices are installed on or inserted in a larger device such as a rocket or a flare. The plug used is permanently attached to the leads leading to the squib or igniter and is normally positioned on the rocket or flare for easy access by the operating personnel after installation.

The plug is usually in the form of a male connector having two or more pins or prongs which are shunted by some type of shorting means during shipping, storing and installation. Oftentimes the simple expedient of weaving a conductive wire about the pins is used. However, there is the danger during handling that the wire may unwind, rust or fall off. To acquire a more reliable shorting device, fcmale plugs that mate with the male connector are internally wired to form a shunt and have proven to be satisfactory. These plugs are usually of elaborate and relatively expensive construction, having keyways or guides to align the female socket and containing threaded or other connecting means. Accordingly, the male counterpart must now include additional mating features such as the keys to fit the keyways and the corresponding connecting means. A further disadvantage is that a variety of male plugs are used which can vary, for example, in diameter and in the number or location of the prong and, therefore, require an equal number of different female shorting plugs.

Accordingly, it is an object of the invention to provide a shorting plug that overcomes many of the disadvantages of the shorting plugs presently used in the art by a relatively simple construction that permits its use with a variety of male connectors.

Another object is to provide a shorting plug that can be used with a variety of male plugs that ditter in the number or position of the pins.

A further object is to provide a shorting plug that can be used with a variety of male plugs that range in diameter sizes.

A still further object is to provide a relatively inexpensive, reusable shorting plug capable of accommodating a variety of male plugs.

Other objects of the invention will become apparent from an inspection of the specification in conjunction with the drawings wherein FIGURE 1 is a longitudinal cross-section of an embodiment of the present invention.

FIGURE 2 is a longitudinal cross-section of the embodiment of FIGURE 1 in mating relationship With a male plug.

FIGURE 3 is a cross-section taken on line 3-3 of FIGURE 2.

FIGURE 4 is a longitudinal cross-section of another embodiment of the present invention.

Generally, the present invention is directed toward a female shorting plug composed of a cylinder or cup filled to a suitable depth with an electrically-conductive material into which the male connector pins are inserted. The mass of the material is not a continuous solid but instead is formed with interstices therein such that it yields or parts when penetrated by the male pins. The material offers a low-resistance, continuous electrically-conductive connection between all of the male pins and eliminates the need for a key and guideway system. Additionally, the cylinder or cup may be metallic and of such a diameter that it abuts the lateral surfaces of the peripheral male pins, thus aiding in the shorting capability.

FIGURE 1 shows an embodiment of the invention in longitudinal cross-section having a metallic cylinder or cup 10 which terminates at one end in a flange 12. The flange 12 is seated in a resilient cap or container 14 which can be molded with the flange 12 in place or can be pro vided with an annular groove or recess into which the flange 12 can be inserted. The cap 14 is composed of a base portion 16 and a forwardly extending side portion 18 concentric about the cup 10 and which terminates in an inwardly projecting annular flange 20.

Positioned within the cup 10, preferably across its entire width, is a yieldable, penetrable, electrically-conductive material 22 bonded to the base 16 of the cap 14 by a suitable bonding compound 24 such as glue, epoxy resin or other adhesive, depending on the material 22 used. The material 22 is formed with interstices therein and, for example, can be a mass of filamentous or expanded metal such as steel wool, spun aluminum or metal sponge, or a cellular polymer such as foamed polyurethane or foamed rubber loaded prior to foaming with metal particles. The depth or thickness of the material along the longitudinal axis may vary depending on the material used, the criterion in all cases being the provision of a continuous conductive path between the various male pins that will penetrate the material. Thus, it is not contemplated that in every case the pins will have to be inserted completely into the material. For example, it may be found that the desired shorting capability is achieved by filling the cup 10 only part way as shown in FIGURE 2. Here it is seen that the male pins are in contact with the material along only a portion of their length. It for safety reasons it is felt advisable to have complete insertion, then the length of the cup 10 and the depth of the material 22 therein can be constructed so as to achieve this end.

A thin foil seal 26 is positioned against the exposed face of material 22 and is attached by a suitable bonding agent to the inner wall of cup 10 to aid in retaining the material within the cup. An annular O-ring groove 28 is located on the inside of side portion 18.

FIGURE 2 shows a longitudinal cross-section of the shorting plug described in FIGURE 1, in intimate contact with a male plug or connector, designated by the numeral 30, and FIGURE 3 shows a cross-section taken on line 3-3 of FIGURE 2. The male connector shown in this case has one center pin 34 and four equally spaced peripheral pins 36. The male connector, forming no part of the present invention, is of conventional construction and has a cylindrical metallic body 32 in which the pins 34, 36 are located. The pins are seated in a rubber or phenolic plug 38 and are soldered or otherwise connected to wire leads (not shown) which are carried to the ignition or explosive device in the form of a cable 40. Adjacent to the mating end of male connector 30 are three exteriorly positioned retaining pins 42 which extend laterally from the connector body 32 for a short distance.

When it is desired to short out the male connector 30, the male plug is inserted into the shorting plug. During insertion, the interior side Wall of cup 10 slidingly abuts the peripheral male pins 36, and all of the pins pierce the foil seal 26 and penetrate the material 22. The material 22 yields or parts as the pins penetrate, but remains in close contact with them on all portions positioned within the material. The side portion 18 of resilient cap 14 is made flexible to permit passage of annular flange 20 over the retaining pins 42 on the male plug. After the flange 20 clears the pins 42, the side portion 18 snaps back to its normal diameter so that the flange 20 overlap the pins 42 to retain the plugs in mating position. An O-ring 44 seated in the slot 28 is compressed during the inserting operation to seal the connection.

As assembled, the peripheral pins 36 and the center pin 34 are in an electrically-conductive interconnected relationship through the material 22. Additionally, the peripheral pins 36 are electrically interconnected due to their tight fit against the interior wall of metallic cup 10. Thus, all of the male pins are in shorting relationship with one another and a low-resistance shunt path between any two or more pins is offered to any current that develops in the leads leading to the ignition or explosive device.

Removal of the shorting plug from the male connector is easily accomplished by flexing the wall portion 18 until the flange 20 clears the upper limit of the retaining pins 42 and then sliding the plug out of engagement with the connector. The foil seal 26 hinders any tendency of the material 22 to unravel or dislodge during the removal operation.

Once separated, the shorting plug is capable of reuse, the procedure being the same as previously described. Since the plug has no keyways or guides that require it to assume the same circumferential position on the male connector each time it is used, it is a simple matter to position the plug circumferentially prior to connection if it is desired not to have the male pins enter the material 22 in the identical position used during the previous connection. However, where the material exhibits elastic properties, there will be a tendency for the material by flexing, springing or otherwise to eliminate partially or completely the holes where the male pins were located during the previous use.

Oftentimes there is no need for the shorting plug to be sealed from the elements or to have external retention means, and, accordingly, the resilient cap 14 can be eliminated. Such an embodiment is shown in longitudinal cross-section in FIGURE 4. The cup 10 is enclosed at 46 and the material 22 is attached thereto by bonding compound 24. During the mating operation, the interior side wall of cup 10 slidingly abuts the peripheral male pins. The close fit between the pins and the wall retains the male and female plug in mating position.

Instead of using a conductive metal in the various embodiments, the cup 10 can be made of a non-conductive material such as cardboard or plastic. In this particular construction, the entire shorting capability is obtained through the material 22.

For any given inner diameter of the cup 10 the shorting plug can be used for those male connectors whose pin grouping has a diameter equal to or less than the cup diameter. When the diameter of the pin grouping is equal to the inner diameter of the cup, then, as explained, the interior side wall of the cup will abut the male pins and, if the cup is made of conductive material, will aid in the shorting operation. If the diameter of the pin grouping is less than the diameter of the cup, then the shorting will be obtained through the material 22. In the embodiment of FIGURE 4, when the diameter of the pin grouping is less than the diameter of the cup 10, the connection is maintained by the close fit between the material 22 and the male pins inserted therein.

While specific embodiments of the invention have been described, it will be obvious to one skilled in the art that various modifications can be made without departing from the spirit of the invention. An example of such a modification is where the bonding compound 24 can be replaced by the inherent bonding capability of certain foamed material, or where the cap 18 is made without the flange 20 and slides onto the male connector in a tight fit. Thus, it is not intended to limit the scope of the invention except as defined by the following claims.

I claim:

1. A shorting plug for the pins of an electrical device comprising an electrically-conductive cylinder closed at one end and open at the other to receive a plurality of pins, said cylinder having a diameter such that said cylinder abuts at least two of said male pins when said plug is in mating relationship with said device, a penetrable, electrically-conductive material attached within said cylinder at the closed end and constructed of suflicient axial thickness to supply an electrically-conductive path to all penetrating pins, and a thin, penetrable seal attached to said cylinder and abutting the exposed face of said material.

2. A shorting plug for the pins of an electrical device comprising a conductive receptacle having a closed end and an open end for receiving a plurality of pins, a penetrable, electrically-conductive material positioned within said receptacle, said material being of sufficient axial thickness to insure an electrically-conductive path between said pins when said plug is in mating relationship with said plurality of pins of said electrical device, a container for said receptacle concentric therewith and attached thereto, and means on said container for connecting said plug to said electrical device.

3. A shorting plug as defined in claim 2 wherein said receptacle is cylindrical and said material is a filamentous metal.

4. A shorting plug as defined in claim 2 wherein said container is made of a resilient material and said connecting means comprises an inwardly directed annular flange adapted to engage said electrical device in a snap fit.

5. A shorting plug as defined in claim 3 further comprising a thin, penetrable seal attached to said cylinder and abutting the exposed face of said material.

References Cited by the Examiner UNITED STATES PATENTS 537,920 4/95 Faulkner 339118 1,743,888 1/30 Hamister 339-94 X 1,909,248 5/33 Benkelman 339-400 X 2,086,548 7/37 Handforth 10228 2,255,838 9/41 \Vells 339118 2,313,379 3/43 Wood 252512 X 2,377,804 6/45 Narvarte 102-28 2,802,421 8/57 Home et a1 10228 2,974,590 3/61 Rarner 10228 3,059,576 10/62 Haefner 10270.2 X 3,064,229 11/62 Dee et a1 339118 FOREIGN PATENTS 176,897 12/53 Austria.

436,397 1/12 France.

1,013,919 5/52 France.

343,468 2/ 31 Great Britain. 490,013 8/38 Great Britain.

JOSEPH D. SEERS, Primary Examiner. 

2. A SHORTING PLUG FOR THE PINS OF AN ELECTRICAL DEVICE COMPRISING A CONDUCTIVE RECEPTACLE HAVING A CLOSED END AND AN OPEN END FOR RECEIVING A PLURALITY OF PINS, A PENETRABLE, ELECTRICALLY-CONDUCTIVE MATERIAL POSITIONED WITHIN SAID RECEPTACLE, SAID MATERIAL BEING OF SUFFICIENT AXIAL THICKNESS TO INSURE AN ELECTRICALLY-CONDUCTIVE PATH BETWEEN SAID PINS WHEN SAID PLUG IS IN MATING RELATIONSHIP WITH SAID PLURALITY OF PINS OF SAID ELECTRICAL DEVICE, A CONTAINER FOR SAID RECEPTACLE CONCENTRIC THEREWITH AND ATTACHED THERETO, AND MEANS ON SAID CONTAINER FOR CONNECTING SAID PLUG TO SAID ELECTRICAL DEVICE. 